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4 μ m PET aluminum plated film · ultra-thin capacitor and composite current collector
In the design of metalized thin film capacitors and composite current collectors, the thickness of the dielectric film directly determines the volumetric efficiency of the device - the thinner the film, the greater the capacitance per unit volume, and the lighter the weight of the device. Over the past few decades, the thickness of PET film has gradually decreased from the early 50 μ m and 25 μ m to 12 μ m, 6 μ m, and 4.5 μ m, and has now advanced to 4 μ m.
What is the concept of 4 μ m? As a reference, the diameter of a standard adult hair is approximately 60-80 μ m. The thickness of 4 μ m PET film is only about one fifteenth of the diameter of a hair. At this scale, PET film is approaching its physical limit as an independent film - thinner means facing significant process challenges in processes such as coating, slitting, and winding.
Core Insights:It is precisely this "extreme thinness" that makes 4 μ m PET aluminum plated film irreplaceable in applications such as metalized thin film capacitors, lithium battery composite current collectors, and precision electronics that require extreme miniaturization.
The aluminum layer preparation of 4 μ m PET aluminum plated film adopts vacuum evaporation process - in a highly vacuum environment, high-purity aluminum is heated to the evaporation temperature (about 1200-1400 ° C), and the aluminum vapor is condensed and deposited on the surface of the high-speed running PET film, forming a layer of metallic aluminum. The thickness of the aluminum layer is usually in the range of 20-100 nanometers (200-1000 Å).
Vacuum deposition on ultra-thin substrates with a thickness of 4 μ m faces a series of technical challenges that are far more stringent than conventional thickness substrates:
4 μ m PET has extremely low thermal capacity and requires precise control of evaporation temperature, speed, and substrate speed to prevent shrinkage, warping, or melting.
The mechanical strength of extremely thin substrates is limited, and a precise low tension control system is the core threshold for mass production.
Any small defect can become a penetrating pinhole, and low pinhole aluminum coating is a core requirement for high-end capacitors and composite current collectors.
Accurately regulate the evaporation rate and substrate speed to achieve nanoscale control of aluminum layer thickness.
PET is one of the most common dielectric materials in metallized film capacitors. PET film has a high dielectric constant and excellent self-healing properties, with a working temperature of up to 120 ° C. The standard thickness coverage range for metallized PET film capacitors is from 1.9 μ m to 12 μ m, with 4 μ m located at the core of this extremely thin range.
The core engineering value of 4 μ m PET substrate lies in its volumetric efficiency. The capacitance of a capacitor is inversely proportional to the thickness of the dielectric - the thinner the film, the greater the capacitance within the same volume. For thin film capacitors that require stable operation in high current and high ripple scenarios, a 4 μ m ultra-thin PET substrate can achieve higher capacitance density in a limited space.
Process collaboration:The internal electrodes of metallized film capacitors are ultra-thin metal layers deposited on the surface of the film through vacuum coating technology. The combination of 4 μ m PET substrate and nanoscale aluminum coating has pushed the miniaturization of capacitors to a new height. Metallized PET film capacitors are widely used in fields such as consumer electronics, automotive electronics, and industrial power supplies.
The application of 4 μ m PET aluminum coated film in the field of lithium battery composite current collectors is one of the most concerned technological directions in recent years.
Traditional lithium battery positive electrode current collectors use aluminum foil. The composite aluminum foil adopts a sandwich structure of "double-sided aluminum plating on polymer base film" - a 4 μ m thick PET film in the middle, with 1 μ m aluminum layer on each side, for a total thickness of 6 μ m. The key advantages of composite aluminum foil are reflected in three dimensions:
PET composite aluminum foil significantly reduces the weight of the current collector and directly converts it into an increase in battery energy density.
Polymer based materials are flame retardant, and the conductive layer melts to form a "point break" when short circuited, reducing the risk of thermal runaway.
The amount of aluminum used is much lower than that of pure aluminum foil, and the material cost advantage is significant.
Manufacturing process:First, a 50-80nm metal layer is deposited on the surface of a 4 μ m PET film using magnetron sputtering and vacuum evaporation, and then thickened to 1 μ m by electroplating with water. Advanced Institute Technology can provide customized PET aluminum plated film products with a thickness of 4 μ m and controllable square resistance.
Based on a 4 μ m PET substrate, aluminum plated film products with different aluminum layer thicknesses can be prepared by precisely controlling the evaporation process parameters. The thickness of the aluminum layer (characterized by optical density OD value) ranges from 0.1 to 1.0, and different thicknesses correspond to different performance focuses:
| Product Type | Optical density (OD) | Aluminum layer thickness | Key Features | Typical Applications |
|---|---|---|---|---|
| 4 0.1PET aluminum plated film | ~0.1 OD | Ultra thin aluminum layer (<20nm)<> | Extremely flexible, semi transparent, and lowest material cost | Ultra thin capacitors, precision optical films, low barrier packaging |
| 4 0.3PET aluminum plated film | ~0.3 OD | Thin aluminum layer (~30nm) | Good flexibility and moderate barrier properties | Metallized film capacitors, electronic shielding |
| 4 1PET aluminum plated film | ~1.0 OD | Thicker aluminum layer (~100nm) | High reflectivity, low surface resistance, high barrier properties | Lithium battery composite current collector, high-end capacitor, EMI shielding |
Note: The higher the optical density (OD) value, the thicker the aluminum layer, and the higher the barrier and reflectivity. The thickness of the aluminum layer is usually in the range of 20-100 nanometers.
Selection suggestion:The lower the OD value, the better the flexibility and the stronger the winding adaptability; The higher the OD value, the stronger the conductivity and barrier properties. Balancing capacitance density, flexibility, and barrier requirements comprehensively.
4 μ m is one of the ultra-thin specifications that can be mass-produced for PET film, covering 3.1-188 μ m, which is at the extreme low-end.
20-100 nanometers, the thicker the barrier and conductivity, but the flexibility decreases.
The surface resistance can be as low as 0.7 Ω/sq, and the visible light reflectivity is ≥ 95%.
The oxygen/water vapor permeability is reduced by more than 99%, and the long-term use temperature is 120 ° C.
One of the core applications. The standard specification is 2-12 μ m thickness, and 4 μ m achieves higher capacitance density. It is widely used in consumer electronics, automotive electronics, and industrial power supplies.
The fastest growing field. 4 μ m PET base film double-sided aluminum plating replaces traditional aluminum foil, improving safety, energy density, and cost advantages.
Ultra thin shielding layer, suitable for small spaces, with low surface resistance and excellent shielding performance.
Reflectivity ≥ 95%, used for optical reflective films, building insulation films, and automotive thermal management.
The higher the OD value, the stronger the barrier and conductivity. Capacitor selection based on voltage/capacity; The composite current collector needs to ensure that the surface resistance meets the requirements.
Ultra thin substrate pinhole control is a core quality indicator, and high-voltage capacitors and composite current collectors have strict requirements for pinhole density.
4 μ m film is prone to wrinkling and fracture, and its compatibility with existing equipment needs to be evaluated. Advanced technology supports flexible customization.
The long-term use temperature of PET is 120 ° C, and if it exceeds this, higher temperature resistant substrates such as PEN or PI should be considered.
The essence of 4 μ m PET aluminum coated film is an engineering product that pushes the thickness of PET film to its physical limit. It is not simply "thinning" - at the 4 μ m scale, material tension control, temperature management, pinhole suppression, and coating uniformity all face engineering challenges that are far more stringent than conventional thickness substrates. It is precisely these boundary conditions that have been overcome one by one that enable the 4 μ m PET aluminum coated film to move from the laboratory to mass production, becoming the core material for high-end applications such as metalized thin film capacitors, lithium battery composite current collectors, and precision electronics.
From improving the volumetric efficiency of thin film capacitors to upgrading the safety of lithium battery composite current collectors, the 4 μ m PET aluminum plated film is transforming the simple engineering goal of "thinner" into tangible performance improvements and cost optimization. For engineers, understanding the process constraints and performance opportunities behind the thickness of 4 μ m - why it is 4 μ m instead of thinner, and how to choose the OD value - is more valuable than simply remembering a specification.
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